INES-event
INES 1

Found radioactive source

On 28 Sep 2011 evening, a citizen equipped by the chance with a special watches with dosemeter, informed the Police of the Czech Republic that there was an increased radiation on a children playground in Prague 4. By activating the integrated emergency services the police and fire brigade arrived to the location. The increased radiation was confirmed, State Office for Nuclear Safety (SONS) dispatched a mobile group of National Radiation Protection Institute, which measures the radiation and identified the source. The amounts of dose were approx. 130-140 microSv/h in 1 m, 1mSv/h 25 cm above the source. With increasing distance from the source the amounts decreased down to the level of natural background. The zone of increased radiation was marked and the place was guarded by the police. On 29 Sep early morning the mobile group arrived again to perform an in-depth measurement. The State Office for Nuclear Safety managed the activities and finally called a specialised licensed company ÚJV ?e?, a.s. that identified the source, extracted the source from the ground and transported it to the laboratories for further analysis. It was an object of a cylinder-like shape approx. 2,8 cm long with a diameter of 0,5 cm containing a sealed radiation source 226Ra. After the source had been transported away, the play ground was measured again and the increased radiation fell down to normal levels. The ground was made accessible to the public. ÚJV ?e? found out that the dose directly in the cylinder was about 150 mSv/h, in 1m then 150 micro Sv/h, an estimate of activity is about 660 MBq. Based on current findings it is very probably a source 226Ra that was used in radiotherapy in the past. The further analysis of the source didn't help up to now to find a potential owner of the source there was not an identification found after the cleaning of source surface. Concerning the doses of public - SÚJB analysed the situation retrospectively, and the doses of public were estimated. Based on a very conservative approach it was assumed that if anyone had spent about 1 hour a day whole year (regardless winter, rain) in the closes place, which was a bench close to the location of the source, an estimation of the dose would have been 3,5 mSv/year, which is a dose received yearly from natural background in the Czech Republic. On 5 October, SONS organised in cooperation with District Council of Prague 4 a meeting with parents, who regularly visited the play ground and were interested in obtaining more information mainly about the potential impact of the radiation on their children's health. Several scenarios that considered length, place, age of children and possible geometry of radiation were presented at the meeting. A physician of SONS explained principles of biological effects of ionizing radiation and answered questions of participating mothers. The physician concluded that the doses were in the order of mSv, no more than 30 mSv/y for the worst case scenario when the child was staying most of the time directly on the spot where the source was found and that any health impacts could not be anticipated.

Location: Praha
Event date: Wed, 28-09-2011
Nuclear event report
Legenda & explanation